Developer



Patented Aug. 31, 1937' nnvsnom Leopold D. Mannes and Leopold Godowsky, In,

Rochester, N. Y.,

assllnors, by mesne assignments, to Eastman Kodak Company, Jersey City, N. 1., a corporation of New Jersey No Drawing. Application February 27, 1935,

. SerlalNo. 8,518

14 Claims.

This invention relates to photographic developers. and, more particularly, to developers having increased reduction potential.

Certain developers, such as the para-phenylenediamines, are unsatisfactory for ordinary photographic use because of their low reduction potential. In the production of natural color photographic plates or films, it is frequently desirable to use the para-phenylenediamines as developers and to form the colored image by coupling during developing the oxidation'pro'duct of the developer with a color-forming compound. The color-forming compound may be mixed with the developer, or may be incorporated in the sensitized emulsion prior to exposure. Such a process is disclosed in Fischer U. S. Patent No.

1,102,028, June 30, 1914. The para-phenylenediamine developers used in this process have a low reduction potential and it is, therefore, necessary to increase the time of development in order to obtain a satisfactory picture.

It is an object of the present invention to provide a method for increasing the reduction potential of aromatic amino developers, particularly color developers. It is a further object to provide means for decreasing the time of development when using the aromatic amines as developers. It is a still further object to provide means for increasing the color gamma of natural color pictures on development.

These objects are accomplished by the present invention by using thiocyanates mixed with the developer. I

According to our invention a film base coated with two or more silver halide emulsion layers, each of which is sensitized to a different region of the spectrum, is exposed to form a latent colorseparation image in each layer. The film is developed in a developer in which an aromatic amine, such as para-phenylenediamine hydrochloride, is the developing ingredient and which contains a color-forming compound. On development of the latent image, the silver halide present in the emulsion is reduced to metallic silver and where this occurs, the para-phenylenediamine is oxidized. The color-forming compound present in the developer is one which will combine with the oxidation product of the paraphenylenediamine to form a colored dye compound. Since the oxidation product is formed only where the silver halide is' reduced, a dye is formed onlyat such points. This developer when used alone for developing negative films is not entirely satisfactory due to the length of time required for the development. We have found that by adding a small amount of a thiocyanate,- such as potassium thiocyanata'to the developer, the reductionxpotentlal'of the developer is increased to such an extent that a development takes place in the time ordinarily.required for 5 development by the use of a metol-hydroquinone type 01' developer.

The following formulas illustrate developers which may be used according to our process.

Formula 1 produces on development a blue-green 10.

image and Formula 2 produces a magenta image.

Water to make cublc centimeters" 1000 (I?) (Added to ((1)) Brom-thioindoxyl gram 1 Methanol cubic centimeters Various thiocyanates, such as potassium, sodi- 35 um and ammonium may be used.

Our invention is applicable to the formation of color pictures by any method in which a color is formed by coupling of the oxidation product of an aromatic amine developer with a color former. The sensitized emulsion may be in one or more layers and may be on one or both sides of a film. Our process may also be used with plates as well as films and with various types of color separation processes, for example, in which the 45 color separation negatives are exposed separately and later superposed to form a complete colored picture. 'Ihe 'colorforming compound may be present in the developer solution or it may be incorporated in the emulsion layer prior to exposure.

Our invention is not limited to the use of thiccyanates with color developers. We have found that a small amount of thiocyanate will increase the reduction potential of an aromatic amino quarter to 2 grams per liter of developer solution, while with ordinary para-phenylenediamine developers, amounts as high as 7 grams per liter have been used.

In referring to the aromatic amino developers, we intend to include the mono-, di-, and triamino aromatic compounds, of which the paraphenylenediamines are the compounds generally used. The salt form, such as the hydrochloride or the sulfate, is most desirable, due to its stability in the dry state. These compounds may be substituted in the amino group or in the ring, forming the alkyl phenylenediamines, and the toluylenediamines.

A particular advantage of our process is the fact that it enables the direct development of color films to form a colored image. It is frequently necessary with such films to develop the film in an ordinary meto'l-hydroquinone developer to a black and white image and later convert this image by color development to a colored image. By the use of our method in which thiocyanates are added to the developer, the colored image may be obtained by direct development.

Our invention is not limited to the specific examples disclosed, but may be used in numerous other forms and modifications.

Having thus described our invention, what we declare is new and desire to secure by Letters Patent of the United States is:

1. A process of producing a colored photographic image which comprises developing a latent image in an alkaline solution containing a primary aryl amine developing agent, said aryl being of the benzene series, and a thiocyanate, and simultaneously coupling the oxidation product of the primary aryl amine developer with a color-forming compound. v

2. A process of producing a colored photographic image which comprises developing a latent image in an alkaline solution containing a para-phenylenediamine and a thiocyanate, and simultaneously coupling the oxidation product of the para-phenylenediamine with a color-form ing compound.

3. A process of producing a coloredphotographic image which comprises developing a latent image in an alkaline solution containing a para-phenylenediamine and a thiocyanate, and simultaneously coupling the oxidation product of the para-phenylenediamine with a color-foaming compound originally present in the developer solution.

4. A process of producing a colored photographic image which comprises developing a latent ima'ge in an alkaline solutionto which has been added a p'ara-phenylenediamine' hydrochloride and a thiocyanate, and simultaneously coupling the oxidation product of the para-phenylenediamine with a color-forming compound.

5. A process of producing a, colored photographic image which comprises developing a latent image in an alkaline solution to which has been added a para-phenylenediamine hydrochloride and a thiocyanate, and simultaneously coupling the oxidation product of the para-phenylenediamine with a color-forming compound originally present in the developer solution.

6. Aprocess of producing a colored photo'- graphic image which comprises developing a. latent image in an alkaline solution containing a para-phenylenediamine and an alkali thiocyanate, and simultaneously coupling the oxidation product of the, para-phenylenediamine with a color-forming compound.

7. A process of producing a colored photographic image which comprises developing a latent image in an alkaline solution containing a para-phenylenediamine and potassium thiocyanate and simultaneously coupling the oxidation product of the para-phenylenediamine with a color-forming compound.

8. A process of producing a colored photographic image which comprises incorporating a color-forming compound in a sensitive emulsion, exposing said emulsion to form a latent image, and developing said latent image in a developer containing a para-phenylenediamine and a thiocyanate. I

9. A process of producing a. colored photographic image which comprises incorporating a color-forming compound in a sensitive emulsion, exposing said emulsion to form a latent image, and developing said latent image in a developer containing a para-phenylenediamine salt and potassium thiocyanate.

10. A photographic developer comprising a para-phenylenediamine in alkaline solution, a color-forming compound and a thiocyanate.

11. A -photographic developer comprising a para-phenylenediamine in alkaline solution, a color-forming compound and an alkali thiocyanate.

12. A photographic developer comprising a para-phenylenediamine inorganic acid salt in alkaline solution, a color-forming compound, and

a thiocyanate.

13. A photographic developer comprising a para-phenylenediamine hydrochloride in alkaline solution, a color-forming compound and a thiocyanate.

14. A photographic developer comprising a para-phenylenediamine salt in alkaline solution, a color-forming compound and potassium thiocyanate.

LEOPOLD D. MANNES. LEOPOLD GODOWSKY, JR. 

